Serpentine accessory drive systems are widely used on various vehicle engines including automotive, industrial, truck and bus. A typical serpentine drive system includes a driving pulley on the crankshaft of the vehicle engine. A belt is trained on a series of driven pulleys for the accessories. An advantage of the serpentine drive is that, by providing an automatic belt tensioner in the system, the accessories can be fixedly mounted instead of requiring a means of adjustment to properly tension the belt.
The engine crankshaft by its periodic pulse nature establishes a highly dynamic loading on the belt. This high dynamic loading is due to the variable torque output characteristics of internal combustion engines. The tensioner cannot accommodate all of the variable torque characteristics which causes fluctuations in the belt tension. The result can be noise and decreased belt life due to instantaneous belt slippage between the belt and the pulleys about which it is trained.
Engine crank shaft decouplers are used to deal with the high dynamic belt loading. Generally, the decoupler must have a capacity equal to the system capacity.
Representative of the art is U.S. Pat. No. 5,139,463 to Bytzek et al. which discloses a serpentine belt drive system for an automotive vehicle in which the sequence of driven assemblies includes an alternator assembly comprising a housing and an armature assembly mounted in the housing for rotation about an armature axis. A hub structure is carried by the armature assembly outwardly of the housing for rotation therewith about the armature axis. A coil spring is disposed in operative relation between the alternator pulley and the hub structure for transmitting the driven rotational movements of the alternator pulley by the serpentine belt to the hub structure such that the armature assembly is rotated in the same direction as the alternator pulley while being capable of instantaneous relative resilient rotational movements in opposite directions with respect to the alternator pulley during the driven rotational movement thereof.
What is needed is a damped isolator comprising a first pulley connected to a first hub and an elastomeric isolator disposed between the first hub and a one-way clutch, the one-way clutch connected to a second pulley. The present invention meets this need.